This invention relates, in general, to an improved septic tank system, and more particularly, to an improved outlet which may be readily installed in an existing septic tank of such systems without material alteration thereof, for handling wastes and sewage from industrial, commercial, and residential installations in rural areas where public disposal systems are not available.
These systems comprise essentially, a septic tank in which wastes and sewage are collected, the larger solid particles being divided into smaller particles, partly digested, and the resulting effluent discharged into a drain field.
The septic tank in such systems may vary in size and shape but usually is in the form of a closed rectangular box, preferably of concrete, although other materials, such as metal, are used in some systems. The size of the tank should be sufficient to provide a liquid depth of from 21/2 to 5 feet, and of a volume sufficient to handle the anticipated wastes and sewage to be discharged into the tank.
Access to the interior of the septic tank is provided by a removable closure of appropriate size so that the undigested solids which form a layer of sludge at the bottom of the tank can be removed at periodic intervals.
Wastes and sewage are introduced into the upper portion at one end of the tank and discharged at the upper opposite end at a "T", the location of the lateral extension of the "T" determining and maintaining the desired level of liquid in the tank. A similar "T" may be used for the inlet to the tank, the upper open end of the "Ts" permitting any gas therein to pass into the space above the liquid level in the tank.
In operation, upon introduction of wastes and sewage through the inlet of the tank, the larger solid particles settle to the bottom of the tank where digestion is effected by fermentation due to the presence of anerobic bacteria, seeding being accomplished when fresh sewage is added. The bacteria involved in the digestion process thrive under anerobic conditions.
While the larger particles of sewage settle and form a layer of sludge on the bottom of the tank, the effluent contains a considerable amount of finer sewage particles in suspension. It has been recognized for some time that if effluent containing these finer particles is permitted to pass directly into the drain field, the small particles clog the pores of the drain field and, in time, materially reduce its efficiency. Moreover, the fermentation process results in the formation of large volumes of gas rising through the sludge and effluent, the gas entrapping particles of sludge which are constantly mixed with the effluent before settling to the bottom of the tank. This increases to a marked extent the amount of sludge suspended in the effluent.
In the past means have been provided to remove as far as practicable the suspended particles from the effluent before it is discharged in order to maintain the efficiency of the drain field. The digestion process taking place in the septic tank also results in the formation of considerable amounts of scum which collects on the surface of the liquid within the tank and it is important that means be provided to retain the scum within the tank and prevent its discharge along with the effluent into the drain field.
These problems have been recognized and various means proposed in an effort to overcome these difficulties. Baffles of various forms have been devised to retain the scum within the septic tank and to divert the gas containing entrapped sewage particles away from the tank outlet in order not to impair the efficiency of the drain field.